In Tetrahedron Letters ‘Hydrastine’ reported as ‘Noscapine’
Recently, I came across a paper in reputed weekly chemistry journal, Tetrahedron Letters. It was describing short synthesis of Noscapine and some other natural alkaloids. However, while carefully looking at the structure I found that they have synthesized a molecule which is not Noscapine. When I did a SciFinder investigation for the same I confirmed the molecule synthesized by them was Hydrastine. Initially I thought there may be some error in structure drawing as the methoxy group was missing from the aromatic ring of the isoquinoline ring counterpart of the Noscapine molecule.
The next thing, I did was to check the physical data reported for the synthesized compound which was provided there as reference 25(a) where they reported that the data for the compound (Noscapine, erythro-1a) is in accordance with the one reported in Canadian Journal of Chemistry in 1973.
The 1H-NMR data described in this TL article is lacking the 3 proton’s signal for the aforesaid methoxy group. This led me to look for Can J Chem paper of 1973 and luckily we have access (OA) to that, in their paper they have described Noscapine with its old name Narcotine and clearly indicated the structure of Hydrastine. They haven’t reported any 1H-NMR data for Noscapine or Hydrastine.
It was now clear to me that the paper published in Tetrahedron Letters titled ‘Short synthesis of noscapine, bicuculline, egenine, capnoidine, and corytensine alkaloids through the addition of 1-siloxy-isobenzofurans to imines’ has reported Hydrastine as Noscapine with wrongful citation of an article from Can J Chem. They have also reported the structure of a Noscapine derivative with better anticancer activity, EM 0115 as EM 105.